I am currently "optimizing" a scientific modelling program developed in Fortran 95. This program is basically making heavy computations in 3D to solve some equations, in addition numerous variable have to be saved and used ~ 50 tables with sizes likes (50; 50; 10000), I even have some 5D tables with sizes like (6;6;15;15;10000) to save in order to reduce the computation time.
I developed a perfectly working version of this code using a python3 interface to control my runs. Basically python is calling a fortran module containing my code to obtain all the results from my modelling. The problem with this method is that I cannot parallelize my code in some time consuming regions. Moreover, I would benefit from the computational time advantage of Fortran for a post treatment of the models that is now partially done in python due to interface.
In the first part of my optimization campaign for this code I want to add a control of the runs with Fortran. A program would call the module containing my code to obtain all the necessary and heavy variables. The Python interface would still be presented, the switch between the Fortran and python control run being done in the compilation in the Makefile directly, this Makefile is already done, everything is compiling well and the python interface is still perfectly working.
My troubles are concerning the Fortran control program and its gestion of the allocated memory I assume. As the size of my tables are not known in advance and requires to open some files I have to declare all my variable as ALLOCATABLE. I then allocate them with the correct sizes before calling my module containing my code. When calling my code errors related to memory problems are appearing, with the error message "Program received signal SIGSEV: Segmentation fault - invalid memory reference". This error appears when I'm setting a table to 0d0, if I'm reducing the size/precision of my modelling the program can proceed a bit further before crashing hence the memory related problem. I think that I'm doing something not correct in the utilisation of the variables between my control and my modelling module. Maybe some variables are stored in the wrong memory space, I precise that I'm using gfortran on ubuntu 22.04.1.
I have different possibilities to try to solve this issue using derived types and pointers or simply by breaking my modelling module. Before going into these heavy structural modifications I wanted to know if someone has experience an equivalent problem and what were the solutions. Here is a schema of the structure of my code:
Run program:
program run_model
use coordinates
use file
use mathematical
use modelling_module
implicit none
integer :: n_x, n_y, n_z
real(8),dimension(:), ALLOCATABLE:: x,y,z
+ all other output variables in 3D
.
.
.
Some operations and file opening
ALLOCATE(x(n_x),y(n_y),z(n_z))
+ all other variables
CALL modelling(n_x, n_y, n_z, output variables)
end program run_model
Modelling module in a separated file:
module modelling_module
use coordinates
use file
use mathematical
implicit none
private
public :: modelling
contains
subroutine modelling(n_x, n_y, n_z, output variables)
integer, intent(in):: n_x, n_y, n_z,
real(8),dimension(n_x), intent(out):: x
real(8),dimension(n_y), intent(out):: y
real(8),dimension(n_z), intent(out):: z
+ all output variables
Computation of the model
.
.
.
end subroutine modelling
end module modelling_module
Thank you in advance for your answers !
